1. Field of the Invention
The present invention relates to improvements in the anticorrosion of an iron or steel material coated with an electroplated layer of an Sn base-Zn alloy.
2. Description of the Prior Art
Such anticorrosive coatings applied to such iron and steel materials as plates, pipes, bars or wires as meet respective requirements have been studied and developed. A steel material in which an electroplated layer of an Sn base-Zn alloy containing more than 50% by weight tin (this electro-plated layer shall be merely called on alloy or alloy layer hereinafter) is formed on the surface and a chromate-treatment is applied on said alloy layer is recently practiced. However, such alloy layer requires a long time in forming the required layer thickness or, for example, 20 to 25 minutes in forming a layer thickness of 15 to 20 microns making it unavoidable to reduce the productivity. Thus an improvement of the productivity together with a further improvement of the anticorrosion is hoped for today.